1. Field of the Invention
The invention relates, generally, to pneumatic valve assemblies and, more specifically, to a pneumatic valve having a pilot valve moveably supported in a pilot valve bore formed in the main valve member.
2. Description of the Related Art
Pilot operated pneumatic valves are well known in the art for controlling the flow of pressurized air to and from various pneumatically actuated devices such as press clutches, air brakes, air cylinders or any other pneumatic device or application requiring precise control of operating air. More specifically, two-way, three-way and four-way pilot operated valve assemblies are commonly employed in these environments. Such valves typically include a main valve body with a valve member movably supported within a valve bore in response to air pressure which is directed by a separate pilot valve to one or alternating ends of the valve member. A solenoid actuates the pilot valve to one predetermined position. A return spring or another pilot valve is employed to bias the valve member back to a known position.
Valve assemblies of this type known in the related art typically include a main valve body to which is separately mounted a pilot valve body using fasteners. Valves of this type are employed in a wide variety of manufacturing environments where a high flow rate and very fast response time are desired. As the technology for these valves has advanced, there has been an increase in the demand for smaller valves which are used in tight spaces. Over the years, there have been a number of improvements in this general field which have facilitated high flow rates and fast response times in relatively small valves. Still, there remains a need in the art for even faster and smaller valves. However, the common arrangement wherein a pilot valve is mounted to a main valve has become a design barrier which has affected the size and speed of such valves.
The present invention overcomes these design barriers and other disadvantages of the related art in a pilot operated valve assembly. More specifically, the present invention is directed toward an improved pilot operated valve assembly including a valve body having a pressurized air supply inlet port in communication with a source of pressurized air and at least one cylinder passage. A main valve bore extends axially within the valve body and a valve member is movable between predetermined positions within the main valve bore to selectively direct pressurized air from the inlet port through at least one cylinder passage. A pilot valve bore is also formed within the main valve member and extends coaxially relative to the main valve bore. A pair of short pilot cylinder ports are spaced apart from one another and extend between the main valve bore and the pilot valve bore. A pilot valve member is movably supported between predetermined positions within the pilot valve bore to selectively direct pressurized air from the pilot valve bore through alternating ones of the pilot cylinder ports to act upon the main valve member thereby moving the main valve member between its predetermined positions.
The pilot operated valve assembly of the present invention has distinct advantages over the valves known in the related art. More specifically, it is small, has a low profile and is very thinxe2x80x94in one embodiment only 10 mm wide. Thus, it is easily employed in environments where space is at a premium. The small size and low profile of the pneumatic valve of the present invention is facilitated by the pilot valve being integrated into the main valve body. In turn, this feature is made possible by the position of the pilot valve bore being disposed within the main valve member and coaxial to the main valve bore. The pilot valve bore and the main valve bore are connected by very short pilot cylinder ports which direct fluid flow to and from the main valve bore and immediately adjacent to either side of the main valve member to cycle the main valve member between predetermined positions. These short pilot cylinder ports minimize the volume of air required to be filled and dumped from the ends of the main valve member every time the valve is actuated. This structure results in extremely fast and consistent response times.
Further, because the pilot valve is integrated into the main valve body, various parts including fasteners, gaskets, machining and assembly operations are eliminated. The integrated pilot operated valve assembly facilitates a thin valve having a low profile because, heretofore, it was difficult to mount a pilot valve to a main valve body having only, for example, a 10 mm thickness. The pilot operated valve assembly also has impressive flow efficiency and a short stroke. In addition, the valve assembly of the present invention provides a large flow of fluid therethrough when the main valve member is in either one of its two operating positions. The short stroke feature and compactness of the valve provides an efficiently operating valve which can be actuated by a small size general purpose solenoid with low wattage or high wattage power consumption.